The invention relates to a method for producing a semiconductor configuration that includes at least two semiconductor elements, and to a semiconductor configuration of this kind.
It is already known to produce semiconductor elements, such as optical semiconductor elements, by epitaxially growing a layer structure on an n or p-doped semiconductor substrate. In this process, a plurality of individual components, each with an identical layer structure, is constructed on the semiconductor substrate (wafer); by sawing apart the substrate, these components are then separated into individual component chips. A semiconductor configuration constructed of a plurality of components (such as an optoelectronic transmitter and receiver configuration) is then made by assembling the appropriate component chips.
It is also already known, in the context of CMOS processes, to apply locally n or p-doped surface regions to a semiconductor substrate. The local or regional doping of the semiconductor substrate is attained by ion implantation or thermal doping. The local regions to be doped, such as the source/drain regions of a MOSFET, are defined by a mask applied beforehand.
U.S. Pat. No. 4,614,958 describes an optoelectronic component: that has a light emitter and a light receiver that are installed on the same semiconductor substrate. The lowermost electrically conductive layer, toward the substrate, of the light emitter and of the light receiver communicate electrically with one another via the substrate.
Other component structures that include two or more semiconductor elements electrically communicating with one another via a common semiconductor substrate are described in Published International Patent Application WO 91-18421 A1 and Published, Non-Prosecuted German Patent Application DE 42 05 324 A1.
It is accordingly an object of the invention to provide a method for producing a semiconductor configuration that overcomes the above-mentioned disadvantages of the prior art methods and devices of this general type, in which a semiconductor configuration is produced economically and includes at least two semiconductor elements.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing a semiconductor configuration having at least two semiconductor elements, which includes: a) furnishing a semiconductor substrate having a top side; b) forming at least two differently doped surface regions on the top side of the semiconductor substrate; and c) constructing at least two active layer structures on the at least two differently doped surface regions, each of the at least two active layer structures having a plurality of layers including a lowermost electrically conductive layer disposed closest toward the semiconductor substrate, the lowermost electrically conductive layer of each of the at least two active layer structures being electrically separated from one another.
By embodying the two differently doped surface regions on the top side of the semiconductor substrate, it is attained that the two active layer structures, one of which is disposed on each of the doped surface regions of the semiconductor substrate, are not electrically short-circuited via the semiconductor substrate as a result of the different doping of the surface regions. This makes it possible to trigger the two layer structures electrically separately and thus to embody semiconductor elements that can be operated independently of one another on one and the same semiconductor substrate.
By the electric decoupling, achieved according to the invention, of the semiconductor elements, even integrated semiconductor configurations with substantially more than two semiconductor elements can be constructed in a simple way. Sawing the semiconductor substrate apart to separate the semiconductor elements, which was previously necessary, and the ensuing assembly step in which the individual semiconductor elements are put together from a plurality of components to make the desired semiconductor configuration can thus be dispensed with.
The term xe2x80x9csemiconductor componentxe2x80x9d used here should be understood in a broad sense. It covers all kinds of single-function semiconductor structures, such as laser diodes, receiver diodes, etc.
The differently doped surface regions on the top side of the semiconductor substrate can be embodied in various ways. In a first embodiment of the method of the invention, the semiconductor substrate is first completely n or p-doped, and the differently doped surface regions are embodied by applying an epitaxial layer to the top side of the semiconductor substrate, simultaneously or subsequently doping the epitaxial layer with a p or n-doping opposite the doping of the semiconductor substrate, and regionally removing the oppositely doped epitaxial layer. The doping of the epitaxial layer can preferably be done by diffusion of dopant atoms from the gas phase or from a dopant layer deposited beforehand, or by thermal doping in the layer deposition. The surface region doped oppositely from the substrate doping is formed in this case by the surface of the additionally applied epitaxial layer.
A second embodiment of the method of the invention is characterized in that the embodiment of the at least two differently doped surface regions is created by redoping one of the surface regions. This embodiment includes depositing a mask layer on the top side of the substrate. Lithographically structuring the mask layer, in such as way that one of the surface regions to be embodied remains covered by the mask layer, while the other surface region to be embodied is bare. Redoping the bare surface region to a p or n-doping opposite the doping of the semiconductor substrate, or to a nonconductive doping; and removing the mask layer.
The step of redoping is preferably done by diffusion of a dopant substance into the bare surface region of the semiconductor substrate. If the redoping creates a p or n-doped surface region opposite from the n or p-doping of the semiconductor substrate, then dopant gases containing As or P can be used, for instance. To produce a nonconductively doped surface region, H2 can be used as the dopant substance.
The second embodiment has the advantage that no additional epitaxial layer has to be deposited onto the surface; instead, the oppositely doped surface region or the nonconductively doped surface region is created directly on the surface of the semiconductor substrate.
In principle the two layer structures can be built up differently by employing photolithographic structuring processes and etching techniques. In a preferred variant embodiment of the invention, however, the two layer structures are grown simultaneously, as a common layer system, on the semiconductor substrate. The ensuing separation of the layer system into the two layer structures is done by a wet and/or dry etching step and/or by sawing. Since different kinds of semiconductor elements often have an identically constructed active layer system (for instance transmission and reception diodes in optocouplers or laser and monitor diodes in glass fiber applications) a component pair electrically separated from one another can be created in this way. Besides the simplicity of production, already mentioned, another substantial advantage of the integrated construction concept of the invention is that the adjustment step of the two or more semiconductor elements that was previously necessary can now be omitted.
The method of the invention has great variability in terms of the number and configuration of the differently doped surface regions and the structuring of the individual active layer structures. In a preferred variant embodiment of the invention, many differently doped surface regions are embodied in the form of a pattern, in particular a checkerboard pattern, on the substrate surface. This makes it possible to produce large-scale integrated semiconductor configurations in which the semiconductor elements are disposed in a line structure or an array structure on the semiconductor substrate.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for producing a semiconductor configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.